I don't know all the ins and outs of how Vonage works so I'm not sure this applies to you, but here goes.

In my Vonage account there is a place where you can select your call quality (large bandwidth or economy mode). It's a slider thingy. Assuming this feature isn't adapter-specific you should have one too. Just check to see that it is all the way to the right for maximum call quality and you should be trouble free from now on. Well, until the unit goes bad, anyway. Heh heh. (And that happens to all things electronic, so that isn't a desparaging remark aimed at Vonage.)

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